Is it wrong if a guy tells a girl upfront that he isn't interested in a relationship when she never even brought up the idea in the first place?

Some might call that arrogance. I call it better be safe than sorry Reminds me of yesterday:

Is it wrong when a girl talks (a lot ) about sex with a man on a lunchdate, than feeling stupid (ego showing off ) after and having to explain that it wasn't a hint towards him (because it really wasn't)?